ceiling drywall sagging after water leak

Recently, I had a small water leak above my kitchen which soaked a decent sized area of the kitchen ceiling drywall and ceiling joists. After discovering the leak, I removed the insulation, soaked up the water, and started air drying the space. A contractor visited and provided moisture analysis of the affected area and reassured me that the ceiling drywall and joists would be fine, as long as they continued to dry out.

Now, several days later, looking up at the ceiling in the kitchen, I can see moisture affected areas where the drywall was fastened to the ceiling joists. The fasteners look sunken in, the integrity of the drywall right under the studs is softer than its surroundings, and I think the drywall has sagged a little.

My first thought was to sister the ceiling joists and re-fasten the drywall using screws and plaster washers to help pull the dryall back into place, then apply mud to cover the new fasteners and the older, less structurally sound area.

Of course, the ceiling is painted, and my concern is that new plaster won't adhere properly to the ceiling without sanding, etc.

First let it dry several more (post #203111, reply #1 of 1)

First let it dry several more days -- drywall takes longer to dry than you might suspect. Then you can attempt to drive screws about 2" away from the existing, to tighten up the drywall. (Sistering shouldn't be necessary.) If the screw heads sink too easily you can try plaster washers. For sagged areas you may want to fit in additional pieces of framing, either cross pieces or new "joists" midway between the existing, then screw to those.

(Probably too late, but you might have corrected some sagging by tacking boards across the sagged areas to support them while the drywall was still wet.)

If that doesn't result in an acceptable (to you) result then you'll need to cut out the bad spots and fit in patches.

Unless the paint is greasy or unusually glossy, you should have no trouble with mud adhesion, after a light sanding.

Note that "strength" is not a big requirement here -- the drywall just needs to be strong enough to hold up itself.

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